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Low water cut-off (LWCO) wiring and test

Glow Combi C95 & C140

What is going on

LWCO on the Glow C95/C140. Field wired, then tested. A jumper stays on 1 and 2 only when no switch is fitted. Don't leave a jumper in place of a switch you need. The test is what proves the burner drops out on low water.

Likely causes

  • LWCO switch wired to the wrong terminals or wrong wire
  • Factory jumper left across 1 and 2 when a switch is installed, defeating the cutoff
  • LWCO that does not shut the burner down when the water level drops

Check in this order

  1. Leave the factory jumper between terminals 1 and 2 only when no LWCO switch is fitted.
  2. Wire the LWCO switch into the terminal strip as shown in Figure 9.6, using up to 20 ft of 18 ga LVT.
  3. Test the LWCO by lowering the water level and confirm the burner shuts down (see Special Operations, section 11.9).
  4. Restore the water level and confirm the boiler restarts.
  5. Never run the boiler with the cutoff bypassed.

Applies to: C95 & C140

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Source: Glow Brand C95 & C140 installation & operation manual, p. 49. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.